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Review of Alpa A11


Basic specs.

sail specifications
The Alpa A11 is a sailboat designed by the maritime architect John H. Illingworth in the late sixties. The Alpa A11 is built by the Italian yard Alpa.

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Hull

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season.


Rig

The boat equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.


Keel

The Alpa A11 is equipped with a fin keel. The fin keel is the most common keel and provides splendid manoeuvrability. The downside is that it has less directional stability than a long keel.

The boat can enter most marinas as the draft is just about 1.75 - 1.85 meter (5.74 - 6.04 ft) dependent on the load. See immersion rate below.


Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Alpa A11 is 1.57, indicating that this boat could - if evaluated by this formula alone - be accepted to participate in ocean races.


Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.6 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.


Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Alpa A11 is about 137 kg/cm, alternatively 771 lbs/inch.
Meaning: if you load 137 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 771 lbs cargo on the boat it will sink 1 inch.


Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Alpa A11 is 35.3.

Low High 85% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 85% of all similar sailboat designs. This is a comfort value significantly above average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Alpa A11 is 4.12.

Wide Slim 100% 0 50 100
Compared with other similar sailboats it is slimmer than 100% of all other designs. It seems that the designer has chosen a significantly more speedy hull design. This type of design is also referred to as 'needle'.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Alpa A11 is 363 which categorizes this boat among 'heavy cruisers'.

Heavy Light 12% 0 50 100
12% of all similar sailboat designs are categorized as heavier. A heavy displacement combined with smaller water plane area has lower acceleration and is more comfortable.


SA/D (Sail Area Displacement ratio)

SA/D (Sail Area Displacement ratio)
Indicates how fast the boat is in light wind:
- Cruising Boats have ratios 10-15
- Cruiser-Racers have ratios 16-20
- Racers have ratios above 20
- High-Performance Racers have ratios above 24
Sail-area/displacement ratio (SA/D ratio): 14.67


Maintenance

Bottom Paint

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 25m2 (269 ft2).
Based on this, your favourite maritime shop can tell you the quantity you need.

Note: If you use a paint roller you will need more paint than if you use a paintbrush.


Rig

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.



Guiding dimensions of running rig
UsageLengthDiameter
Jib sheet 11.3 m(37.0 feet)14 mm(0.55 inch)
Genoa sheet11.3 m(37.0 feet)14 mm(0.55 inch)
Mainsheet 28.2 m(92.5 feet)14 mm(0.55 inch)
Spinnaker sheet24.8 m(81.4 feet)14 mm(0.55 inch)

Boat owner's ideas

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.



Finally

We are always looking for new photos. If you can contribute with photos for Alpa A11 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.



References